Monthly Archives: August 2017

Consider the entirely hypothetical situation where you are in a physics conference with really bad wifi. Either because the router has a hard limit in the amount of devices that can connect simultaneously, or the bandwidth is too small to handle everyone’s OwnClouds trying to sync, or it is a D-Link. The usual approach is just to be pissed off and and complain to the organizers, to no avail (while ignoring the talks and trying to reconnect like crazy). Here I’d like to describe a different approach, that if not morally commendable at least lead to more results: blackholing.

To blackhole, what you do is to create a hotspot with your phone with the same name, encryption type, and password as the conference wifi. You then disable the data connection of your phone, and turn on the hotspot. What happens is that the devices of the people close to you will automatically disconnect from the conference router and connect to your hotspot instead, since they will think that your hotspot is a repeater with a stronger signal. But since you disabled your data connection, they are connecting to a sterile hotspot, so you are creating a kind of wifi black hole. To the people far from your, however, this is a gift from the gods, as they keep connected to the conference router, and can use the bandwidth that was freed up by the poor souls that fell in your black hole.

The question is, is it moral to do this? Obviously the people who did fall in your black hole are not going to like it, but one thing to notice is that this technique is intrinsically altruistic, as you cannot use wifi either, since you are in the middle of the black hole (and as far as I know it is not possible to defend oneself against it). It is even more altruistic if you like to sit close to your friends, who will then sacrifice their wifi in favour of a more distant acquaintance. It does become immoral if you arrange with a friend to sit close to the conference router, and you blackhole some random people far from it with the specific intent of giving your friend wifi, without caring about the other people who will also get it.

But let’s consider that you don’t have such tribalistic morals, and consider everyone’s welfare equally. Then the question is whether the utility of $n$ people with bad wifi is smaller than the utility of $k$ people with no wifi and $n-k$ people with good wifi, that is, whether
\[ n\, U(\text{bad wifi}) \le k\,U(\text{no wifi}) + (n-k)\,U(\text{good wifi}). \]Now, assuming that the utility is a function only of the bandwidth available, this simplifies to
\[ n\,U(B/n) \le k\,U(0) + (n-k)\,U(B/(n-k)),\]where $B$ is the total bandwidth of the conference router. Therefore, to determine whether blackholing is moral or not we need to find out how people’s happiness scale as a function of the available bandwidth.

One immediately sees that if the happiness scales linearly with the bandwidth, it is indifferent whether to blackhole or not. But to make relevant moral judgements, we need to find out what the actual utility functions are. By asking people around, I empirically determined that
\[ u(x) = \frac{1}{1+\left(\frac{B_0}{x}\right)^2}, \]where $B_0$ is the critical bandwidth that allows people to do basic surfing. Substituting in the previous inequality, we see that blackholing is moral iff
\[ k \le \frac{n^2 – \left(\frac{B}{B_0}\right)^2}{n}, \]which is better understood if we rewrite $\frac{B}{B_0} = fn$, that is, as the fraction $f$ of people that can do basic surfing with the given bandwidth. We have then
\[ k \le (1-f^2)n, \]which shows that if $f = 1$ it is never moral to blackhole, whereas if $f \approx 0$ it always is. In an hypothetical conference held in Paraty with $n=100$ and $\frac{B}{B_0} = 50$, it is moral to blackhole up to $k=75$ people.